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United States Patent |
6,267,012
|
McLaughlin
|
July 31, 2001
|
Tensile specimen test grip
Abstract
Tensile loading is applied to a notched specimen bar through the base of a
fixture grip having a pair of interfitting pieces releasably held
assembled in a fixture position in axial abutment with the base and in
engagement with the specimen bar by means of a pair of fastener bolts, one
of which is loosened so as to act as a hinge accommodating pivotal
displacement of the interfitting pieces from the fixture position upon
removal of the other fastener bolts.
Inventors:
|
McLaughlin; Michael D. (Germantown, MD)
|
Assignee:
|
The United States of America as represented by the Secretary of the Navy (Washington, DC)
|
Appl. No.:
|
288312 |
Filed:
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April 8, 1999 |
Current U.S. Class: |
73/856; 73/831; 73/859 |
Intern'l Class: |
G01N 003/02 |
Field of Search: |
73/856-860,831-833
|
References Cited
U.S. Patent Documents
5297441 | Mar., 1994 | Smith et al. | 73/860.
|
5585570 | Dec., 1996 | Raymond | 73/856.
|
5798463 | Aug., 1998 | Doudican et al. | 73/789.
|
Primary Examiner: Fuller; Benjamin R.
Assistant Examiner: Stevens; Maurice
Attorney, Agent or Firm: Shuster; Jacob
Claims
What is claimed is:
1. In combination with a test specimen, a grip assembly removably attached
to the test specimen in a fixture position, comprising: a base through
which tensile loading is exerted on the test specimen only in the fixture
position; a pair of interfitting pieces in abutment with the base; and
fastener means interconnecting the base with said interfitting pieces for
pivotal displacement thereof relative to the base between said fixture
position in engagement with the test specimen and a release position
disengaged therefrom; said fastener means comprising: two bolts extending
through the base and said pair of the interfitting pieces in spaced
relation to the test specimen, one of said bolts establishing a hinge axis
about which said pivotal displacement of the interfitting pieces occurs
from the fixture position upon removal of the other of the bolts; each of
said interfitting pieces comprising: an intermediate portion having a
recess engageable with the test specimen in the fixture position; and
axially spaced extensions projecting radially from the intermediate
portion having aligned openings through which the two bolts extend.
2. The combination as defined in claim 1 wherein said base extends in axial
alignment with the test specimen between opposite planar sides in abutment
with the interfitting pieces.
Description
The present invention relates in general to the application of tensile load
to specimens for structural testing thereof.
BACKGROUND OF THE INVENTION
Tensile specimens are subjected to dynamic testing at a high rate by
attachment to and release from a testing machine through which an axial
displacement is imposed on the specimen and diametrical displacement
results, with both displacements being recorded. In the case of a notched
cylindrical bar type of tensile specimen, cloverleaf shaped fixture grips
are presently utilized for attachment to and removal of such specimens
from the testing machine. Such fixture grips require complete assembly of
parts during set up by means of four bolt fasteners and extensive
fixturing by reason of which data recording errors are introduced during
high rate dynamic testing operation because of fixture flexure. It is
therefore an important object of the present invention to provide fixture
grips for tensile specimen bars in dynamic test machine installations as
aforementioned, which will decrease set up and removal time between tests
to thereby increase the testing rate as well as to reduce flexure causing
errors.
SUMMARY OF THE INVENTION
In accordance with the present invention, a hinge type of fixture grip is
provided for removable attachment to each axial end of a notched bar type
of tensile specimen within a dynamic test machine installation. Such grip
is formed from three parts consisting of one base piece of uniform
thickness in axial abutment on one planar side thereof with two
interfitting hinge parts held assembled by a pair of bolt fasteners, one
of which is completely removed while the other is partially loosened so as
to act as a hinge pivot for pivotal displacement of the intermitted hinge
parts during set up or removal of the fixture grip from the tensile
specimen bar.
BRIEF DESCRIPTION OF DRAWING
A more complete appreciation of the invention and many of its attendant
advantages will be readily appreciated as the same becomes better
understood by reference to the following detailed description when
considered in connection with the accompanying drawing wherein:
FIG. 1 is a side elevation view of one axial end portion of a notched
specimen bar held fixed in a tensile testing installation by a fixture
grip constructed in accordance with one embodiment of the present
invention;
FIG. 2 is a partial section view taken substantially through plane
indicated by section line 2--2 in FIG. 1;
FIG. 3 is a section view taken substantially through a plane indicated by
section line 3--3 in FIG.2;
FIGS. 4 and 5 are section views respectively taken substantially through
planes indicated by section lines 4--4 and 5--5 in FIG. 1;
FIG. 6 is a front elevation view of a disassembled base piece of the
fixture grip shown in FIG. 1;
FIGS. 7 and 8 are section views respectively taken substantially through
planes indicated by section lines 7--7 and 8--8 in FIG. 6;
FIG. 9 is a front elevation view of a disassembled hinge piece of the
fixture grip shown in FIG. 1;
FIGS. 10, 11 and 12 are section views respectively taken substantially
through planes indicated by section lines 10--10, 11--11 and 12--12 in
FIG. 9; and
FIG. 13 is a front elevation view of the fixture grip illustrated in FIGS.
1-12, in a hinge opened condition removed from the notched specimen bar
shown in FIGS. 1-4.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
Referring now to the drawing in detail, FIG. 1 illustrates an axially
loaded tensile specimen bar 10 of a generally cylindrical shape having an
intermediate notch 12 therein. Each axial end portion of the bar 10 is
received within a fixture grip assembly 14 constructed in accordance with
the present invention. Each grip assembly 14 is associated with a base
stud 16 which is attached to a test machine (not shown) through which
dynamic testing of the bar 10 as a tensile specimen is performed,
including measurement of its axial extension and diametrical contraction.
The structural arrangement of each grip assembly 14 at the opposite axial
ends of the specimen bar 10, to which the present invention relates,
minimizes flexing of the fixturing used on the bar 10 during installation
within the test machine and accommodates the provision of more accurate
measurement and recordation of data by such test machine.
Each grip assembly 14 as shown in FIGS. 1-5 consists of a base piece 18
attached to the test machine by stud 16 and a pair of interfitted hinge
pieces 20 and 22 held in axial abutment with the base piece 18 while in
alignment with an axis 24 of the specimen bar 10 and the stud 16. All
three pieces 18, 20 and 22 of each grip assembly 14 are interconnected by
a pair of threaded bolts 26 having heads 28 at one axial end respectively
abutting the interfitted hinge pieces 20 and 22. Screw nuts 30 are
threaded onto projecting ends of the bolts 26 for abutment with the base
piece 18 as shown in FIG. 5 to hold the three pieces 18, 20 and 22
assembled.
The base piece 18 as shown in FIGS. 6-8, has parallel spaced, oval shaped
planar sides perpendicular to the axis 24. A central cylindrical bore 32
is formed in the base piece 18, of a diameter substantially equal to that
of the stud 16 received therethrough. A pair of cylindrical bores 34 are
also formed in the base piece 18 equally spaced from the central bore 34
for receiving the bolts 26 therethrough.
Each of the intermitted pieces 20 and 22 are of similar construction. As
shown in FIGS. 9-12, the hinge piece 20 is oval shaped along one side edge
36 to match one planar side of the base piece 18 with which it is in
aligned abutment when attached thereto by both of the bolts 26. The other
planar side of the base piece 18 is matched by one side of the other hinge
piece 22. The intermediate portion 38 of the hinge piece 20 extends
axially along its entire width, between side edge 36 and an edge 40 as
shown in FIG. 9. A semi-circular recess 42 is formed in the edge 40. A
similar recess 42' is formed in the other piece 22 abutting the edge 40 of
piece 20, as shown in FIG. 2, to form a cylindrical bore through which the
bar 10 extends into an enclosure 43, as shown in FIGS. 3 and 4, within
which a flanged end portion 45 of the bar 10 is retained.
A pair of axially spaced extensions 44 and 46 extend radially from the
intermediate portion 38 of the piece 20, having aligned openings 48 and 50
formed therein as shown in FIGS. 9, 10 and 11 for receiving one of the
bolts 26 therethrough. Another pair of axially spaced extensions 52 and 54
of the piece 20 extend radially in the opposite direction from the
intermediate portion 38. Such extensions 52 and 54 also have aligned
openings therein as shown in FIGS. 9, 10 and 12 for receiving the other of
the bolts 26 therethrough.
The grip 14 is held assembled in a fixture position as shown in FIGS. 1-5
by the two bolts 26. To disengage the grip 14 from such position in
abutment with specimen bar 10, only one of the bolts 26 is removed and the
other merely loosened so as to enable the hinge pieces 20 and 22 to swing
apart to a disassembly position as shown in FIG. 13. Complete assembly and
disassembly of the three parts 18, 20 and 22 of the grip 14 is thereby
avoided so as to decrease setup and removal time between tests performed
on a specimen bar 10. Also, there is a reduction in the number of parts
heretofore deemed necessary to form the fixture grips performing all of
the test functions associated with that of grip assembly 14 as
hereinbefore described.
Obviously, other modifications and variations of the present invention may
be possible in light of the foregoing teachings. It is therefore to be
understood that within the scope of the appended claims the invention may
be practiced otherwise than as specifically described.
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